Navodila za obdelavo slik
Atmosferska ekstikcija
(Restore this version)
Modified: 9 October 2018, 11:36 AM User: Bojan Dintinjana →
Najprej si pripravim Landoltov katalog standardnih zvezd. Za nas je najprimernejši "UBVRI standards around celestial equator (Landolt, 2009)" odprem v Vezierju in si nastavim za prikaz stolpce "Name, Vma, e_Vmag, B-V, e_B-V, V-R,e_V-R" potem število zadetkov neomejeno (zvezd v celem katalogu je ene 600), potem izpis naj bo "ascii / text plain " in koordinate J2000 in v decimalnem zapisu. Dobim katalog in spravim v urejevalnik teksta:
# VizieR Astronomical Server vizier.u-strasbg.fr
# Date: 2016-09-20T08:06:36 [V1.99+ (14-Oct-2013)]
# In case of problem, please report to: cds-question@unistra.fr
#
#
....
#Name: J/AJ/137/4186
#Title: UBVRI standards around celestial equator (Landolt, 2009)
#Table J_AJ_137_4186_stars:
....
---------- ---------- ----------- ------ ------- ------ ------- ------ -------
_RAJ _DEJ Vmag e_Vma B-V e_B- V-R e_V-
2000 (deg) 2000 (deg) Name (mag) g (mag) (mag) V (mag) (mag) R (mag)
---------- ---------- ----------- ------ ------- ------ ------- ------ -------
007.519138 -46.469492 TPhe I 14.820 0.0026 0.764 0.0032 0.422 0.0036
007.539975 -46.524697 TPhe A 14.651 0.0028 0.793 0.0046 0.435 0.0019
007.540346 -46.456750 TPhe H 14.942 0.0029 0.740 0.0029 0.425 0.0035
007.567971 -46.466269 TPhe B 12.334 0.0115 0.405 0.0026 0.262 0.0020
007.570750 -46.539278 TPhe C 14.376 0.0022 -0.298 0.0024 -0.148 0.0038
....
Nato nekaj deset vrstic na začetku. ki so za komentar izbrišem in še v imenu zvezde zamenjam presledke v podčrtaj. To naredim tako, da v urejevalniku najprej izberem bločna izbira, za blok označim stolpec Name in vse presledke v stolpcu zamenja s podčrtajem. Kar ohranim komentarja ga dam za ograjco:
#-source=J/AJ/137/4186/stars
#_RAJ _DEJ Vmag e_Vma B-V e_B- V-R e_V-
#2000 (deg) 2000 (deg) Name (mag) g (mag) (mag) V (mag) (mag) R (mag)
#---------- ---------- ----------- ------ ------- ------ ------- ------ -------
007.519138 -46.469492 TPhe_I_____ 14.820 0.0026 0.764 0.0032 0.422 0.0036
007.539975 -46.524697 TPhe_A_____ 14.651 0.0028 0.793 0.0046 0.435 0.0019
007.540346 -46.456750 TPhe_H_____ 14.942 0.0029 0.740 0.0029 0.425 0.0035
007.567971 -46.466269 TPhe_B_____ 12.334 0.0115 0.405 0.0026 0.262 0.0020
007.570750 -46.539278 TPhe_C_____ 14.376 0.0022 -0.298 0.0024 -0.148 0.0038
007.576425 -46.522181 TPhe_D_____ 13.118 0.0033 1.551 0.0030 0.849 0.0015
007.582367 -46.409889 TPhe_E_____ 11.631 0.0017 0.443 0.0013 0.276 0.0007
007.595917 -46.397667 TPhe_J_____ 13.434 0.0023 1.465 0.0043 0.980 0.0011
007.707583 -46.556686 TPhe_F_____ 12.475 0.0008 0.853 0.0024 0.492 0.0005
007.734646 -46.390567 TPhe_K_____ 12.935 0.0007 0.806 0.0007 0.473 0.0007
007.767929 -46.380931 TPhe_G_____ 10.447 0.0008 1.545 0.0011 0.934 0.0008
007.925833 +2.628972 PG0029+024_ 15.268 0.0094 0.362 0.0174 0.251 0.0161
008.050637 +1.188133 HD_2892____ 9.360 0.0026 1.322 0.0022 0.692 0.0017
009.584421 -14.998372 BD_-15_115_ 10.885 0.0015 -0.199 0.0014 -0.095 0.0017
010.525504 +5.156503 PG0039+049_ 12.877 0.0020 -0.019 0.0030 0.067 0.0035
013.062787 -10.662803 BD_-11_162_ 11.184 0.0015 -0.082 0.0015 0.051 0.0015
013.308529 +0.767261 92_309_____ 13.842 0.0035 0.513 0.0057 0.326 0.0014
013.318888 +0.808028 92_312_____ 10.598 0.0014 1.636 0.0025 0.898 0.0005
S teleskopom smo slikali tri sekvence: PG1633+099, SA111 in SA112 zato, si v urejevalniku teksta pripravim izvleček za ta tri polja. V katalogu so imena zvezde brez predpone SA:
248.850104 +9.797194 PG1633+099_ 14.396 0.0016 -0.191 0.0021 -0.085 0.0026
248.858267 +9.798108 PG1633+099A 15.259 0.0032 0.871 0.0042 0.506 0.0033
248.884733 +9.841872 PG1633+099G 13.749 0.0016 0.693 0.0012 0.412 0.0012
248.888767 +9.772419 PG1633+099B 12.968 0.0016 1.081 0.0013 0.589 0.0010
248.902971 +9.827872 PG1633+099F 13.768 0.0020 0.878 0.0024 0.523 0.0013
248.905312 +9.771056 PG1633+099C 13.224 0.0017 1.144 0.0008 0.612 0.0010
248.917037 +9.778214 PG1633+099D 13.689 0.0016 0.535 0.0018 0.324 0.0011
248.937850 +9.823481 PG1633+099E 13.113 0.0021 0.841 0.0020 0.484 0.0014
294.315967 +0.182844 111_773____ 8.965 0.0009 0.209 0.0006 0.121 0.0004
294.318154 +0.201544 111_775____ 10.748 0.0010 1.741 0.0007 0.965 0.0006
294.369329 +0.417428 111_1925___ 12.387 0.0015 0.396 0.0012 0.226 0.0005
294.423154 +0.447483 111_1965___ 11.419 0.0018 1.710 0.0037 0.951 0.0010
294.430367 +0.430153 111_1969___ 10.382 0.0017 1.959 0.0014 1.177 0.0008
294.519075 +0.536817 111_2039___ 12.395 0.0021 1.369 0.0028 0.739 0.0021
294.588558 +0.516739 111_2088___ 13.193 0.0014 1.610 0.0042 0.888 0.0018
294.597758 +0.523733 111_2093___ 12.538 0.0025 0.637 0.0035 0.370 0.0032
310.326929 +0.274461 112_595____ 11.352 0.0014 1.601 0.0009 0.898 0.0005
310.508608 +0.318950 112_704____ 11.452 0.0030 1.536 0.0023 0.822 0.0021
310.560762 +0.149917 112_223____ 11.424 0.0007 0.454 0.0006 0.273 0.0005
310.609942 +0.128472 112_250____ 12.095 0.0021 0.532 0.0019 0.317 0.0019
310.647600 +0.122283 112_275____ 9.905 0.0001 1.210 0.0004 0.648 0.0004
310.694804 +0.268911 112_805____ 12.086 0.0006 0.151 0.0007 0.064 0.0006
310.728812 +0.250528 112_822____ 11.548 0.0007 1.030 0.0008 0.558 0.0005
#---------- ---------- ----------- ------ ------- ------ ------- ------ -------
#_RAJ _DEJ Vmag e_Vma B-V e_B- V-R e_V-
#2000 (deg) 2000 (deg) Name (mag) g (mag) (mag) V (mag) (mag) R (mag)
#---------- ---------- ----------- ------ ------- ------ ------- ------ -------
#-source=J/AJ/137/4186/stars
Datoteko shranim pod imenom onlandolt.wcs in je sedaj moj vhodni katalog. Ima vsega 23 standardnih zvezd iz treh sekvenc. Komentarje sem tu prestavil na konec datoteke, ker bo številka vrstice v naprej kar id zvezde.
Posnete slike najprej kritično pregledam, vse slike morajo imeti najprej opravljena osnovno kalibracijo zero, dark, flat. Potem mora biti narejen astrometrični fit. Kaj je že bilo narejeno idimo v glavi slike, pogledamo recimo s programom ds9 File->Display header. Kot običajno pri obdelavah v irafu si pripravim listo mojih slik:
ls -1 *.fts > imlist
končnice .fts odstranim, vrstni red priredim tako, da si sledijo sekvence kot so v mojem vhodnem katalogu:
PG1633+099-B1
PG1633+099-R1
PG1633+099-V1
PG1633+099-V2
SA111-B1
SA111-R1
SA111-V1
SA112-B1
SA112-R1
SA112-V1
SA112-V2
Zdaj po navodilih za aperturno fotometrijo v irafu pripravim parametre: izmerim sigma, fwhm:
apphot> imstat *.fts nclip=7
# IMAGE NPIX MEAN STDDEV MIN MAX
PG1633+099-B1.fts 4137385 376.5 31.36 283. 470.
PG1633+099-R1.fts 4162102 391.6 25.24 316. 467.
PG1633+099-V1.fts 4169006 242.9 21.35 179. 307.
PG1633+099-V2.fts 4161601 683.3 31.31 590. 777.
SA111-B1.fts 4133428 320.3 30.39 230. 411.
SA111-R1.fts 4127106 383.7 26.47 305. 463.
SA111-V1.fts 4092850 801.3 35. 697. 906.
SA112-B1.fts 4158787 149.9 21.44 86. 214.
SA112-R1.fts 4161932 247.5 24.67 174. 321.
SA112-V1.fts 4156765 687.3 32.7 590. 785.
SA112-V2.fts 4159416 420.7 32.98 322. 519.
apphot>
apphot> imexamine PG1633+099-V2
Sigma, ali STDEV je torej za vse slike približno 30 enot in FWHM je 3.2 piksla. Vnesem v datapars:
apphot> datapars
(scale = 1.) Image scale in units per pixel
(fwhmpsf = 3.20) FWHM of the PSF in scale units
(emission = yes) Features are positive ?
(sigma = 30.) Standard deviation of background in counts
(datamin = 100.) Minimum good data value
(datamax = 63000.) Maximum good data value
(noise = "poisson") Noise model
(ccdread = "RDNOISE") CCD readout noise image header keyword
(gain = "GAIN") CCD gain image header keyword
(readnoise = 0.) CCD readout noise in electrons
(epadu = 1.) Gain in electrons per count
(exposure = "EXPTIME") Exposure time image header keyword
(airmass = "AIRMASS") Airmass image header keyword
(filter = "FILTER") Filter image header keyword
(obstime = "MJD") Time of observation image header keyword
(itime = 1.) Exposure time
(xairmass = INDEF) Airmass
(ifilter = "INDEF") Filter
(otime = "INDEF") Time of observation
(mode = "ql")
apphot>
Potem nastavim še parametre za centriranje zvezde. Ker uporabljam zunanji katalog je potrebno povečati največji dovoljen premik pri centriranju zvezde na recimo 9 pikslov. Do razlik lahko pride ztaradi lastnega gibanja zvezd, naš referenčni katalog je narejen za epho 2000, možno je tudi da pride do razlike zaradi zaokrožitve koordinat ali napake v katalogu.
apphot> lpar centerpars
(calgorithm = "centroid") Centering algorithm
(cbox = 8.) Centering box width in scale units
(cthreshold = 0.) Centering threshold in sigma above background
(minsnratio = 1.) Minimum signal-to-noise ratio for centering algorith
(cmaxiter = 10) Maximum number of iterations for centering algorithm
(maxshift = 9.) Maximum center shift in scale units
(clean = no) Symmetry clean before centering ?
(rclean = 1.) Cleaning radius in scale units
(rclip = 2.) Clipping radius in scale units
(kclean = 3.) Rejection limit in sigma
(mkcenter = no) Mark the computed center on display ?
(mode = "ql")
apphot>
maxshift sem nastavil na 9 pikslov. Potem nastavim še prag treshold z ukazom findpars
apphot> lpar findpars
(threshold = 3.7000000476837) Threshold in sigma for feature detection
(nsigma = 1.5) Width of convolution kernel in sigma
(ratio = 1.) Ratio of minor to major axis of Gaussian kernel
(theta = 0.) Position angle of major axis of Gaussian kernel
(sharplo = 0.20000000298023) Lower bound on sharpness for feature detection
(sharphi = 1.) Upper bound on sharpness for feature detection
(roundlo = -1.) Lower bound on roundness for feature detection
(roundhi = 1.) Upper bound on roundness for feature detection
(mkdetections = no) Mark detected stars on the display ?
(mode = "ql")
in še phot parametri:
apphot> lpar findpars
(threshold = 3.7) Threshold in sigma for feature detection
(nsigma = 1.5) Width of convolution kernel in sigma
(ratio = 1.) Ratio of minor to major axis of Gaussian kernel
(theta = 0.) Position angle of major axis of Gaussian kernel
(sharplo = 0.20) Lower bound on sharpness for feature detection
(sharphi = 1.) Upper bound on sharpness for feature detection
(roundlo = -1.) Lower bound on roundness for feature detection
(roundhi = 1.) Upper bound on roundness for feature detection
(mkdetections = no) Mark detected stars on the display ?
(mode = "ql")
apphot> epar phot
image = "@imlist" The input image(s)
skyfile = "" The input sky file(s)
(coords = "onlandolt.wcs") The input coordinate files(s) (default: image.coo.?
(output = "default") The output photometry file(s) (default: image.mag.?)
(plotfile = "") The output plots metacode file
(datapars = "") Data dependent parameters
(centerpars = "") Centering parameters
(fitskypars = "") Sky fitting parameters
(photpars = "") Photometry parameters
(interactive = no) Interactive mode ?
(radplots = no) Plot the radial profiles in interactive mode ?
(icommands = "") Image cursor: [x y wcs] key [cmd]
(gcommands = "") Graphics cursor: [x y wcs] key [cmd]
(wcsin = "world") The input coordinate system (logical,tv,physical,wor
(wcsout = )_.wcsout) The output coordinate system (logical,tv,physical)
(cache = )_.cache) Cache the input image pixels in memory ?
(verify = )_.verify) Verify critical parameters in non-interactive mode ?
(update = )_.update) Update critical parameters in non-interactive mode ?
(verbose = )_.verbose) Print messages in non-interactive mode ?
(graphics = )_.graphics) Graphics device
(display = )_.display) Display device
(mode = "ql")
Pomembno je da nastavim coords in wcsin. Zdaj lahko poženem phot:
apphot> phot
The input image(s) (@imlist):
Centering algorithm (centroid) (CR or value):
New centering algorithm: centroid
Centering box width in scale units (8.) (CR or value):
New centering box width: 8. scale units 8. pixels
Sky fitting algorithm (centroid) (CR or value):
Sky fitting algorithm: centroid
Inner radius of sky annulus in scale units (15.) (CR or value):
New inner radius of sky annulus: 15. scale units 15. pixels
Width of the sky annulus in scale units (10.) (CR or value):
New width of the sky annulus: 10. scale units 10. pixels
File/list of aperture radii in scale units (1.5) (CR or value):
Aperture radius 1: 1.5 scale units 1.5 pixels
Standard deviation of background in counts (30.) (CR or value):
New standard deviation of background: 30. counts
Minimum good data value (100.) (CR or value):
New minimum good data value: 100. counts
Maximum good data value (63000.) (CR or value):
New maximum good data value: 63000. counts
PG1633+099-B1 978.03 957.76 341.8565 19.296 ok
PG1633+099-B1 1023.02 962.92 343.0444 21.091 ok
PG1633+099-B1 1166.35 1205.00 350.205 19.444 ok
PG1633+099-B1 1189.95 821.62 342.4337 18.972 ok
PG1633+099-B1 1265.82 1128.55 349.394 19.620 ok
PG1633+099-B1 1279.84 814.80 348.053 19.284 ok
PG1633+099-B1 1343.65 854.56 351.0456 19.198 ok
PG1633+099-B1 1456.00 1105.43 364.3751 18.885 ok
PG1633+099-B1 328333.8 -50883.6 INDEF INDEF err
PG1633+099-B1 328331.7 -50731.7 INDEF INDEF err
PG1633+099-B1 328605.4 -48976.0 INDEF INDEF err
...
Za velikost, radij zaslonke (Aperture radius) sem izbral 1.5 piksla. Običajno se vzame nekaj manj kot fwhm, torej 3.2/2 = 1.6, tu upoštevam, da je fwhm premer, za zaslonko pa potrebujem radij. Pomembno je, da mi vse zvezde, iz sekvence označi "ok". Zvezde iz druge sekvence označi "err", seveda ker jih ni na tej sliki. Dobim rezultate v datotekah <slika>.mag.1 Datoteke mag so težko berljive, vsebujejo mmnogo podatkov, zato raje naredim izvleček samo za megnitude in napake z ukazom pdump:
apphot> epar pdump
infiles = "@imlist//.mag.1" Input apphot/daophot databases(s)
fields = "id,mag,merr,xairmass,ifilter" Fields to be extracted
expr = "MAG!=INDEF" Boolean expression
(headers = no) Print field headers?
(parameters = yes) Print parameters?
(inlist = "")
(mode = "ql")
apphot> pdump > meritev.txt
V datoteki meritev.txt so zbrani rezultati za vse slike in vse filtre. Najbolje, da ločim posamezne filtre:
$ grep V meritev.txt > V.txt
$ grep R meritev.txt > R.txt
$ grep B meritev.txt > B.txt
Datoteka R.txt izgleda tako:
1 18.668 0.012 1.24078 R
2 19.005 0.015 1.24078 R
3 17.608 0.007 1.24078 R
4 16.664 0.004 1.24078 R
5 17.526 0.006 1.24078 R
6 16.898 0.005 1.24078 R
7 17.618 0.007 1.24078 R
8 16.917 0.005 1.24078 R
11 16.569 0.004 2.076707 R
12 14.968 0.002 2.076707 R
13 14.586 0.002 2.076707 R
....
To so izmerjene instrumentalne magnitude, napaka in zračna masa pri kateri je bila slika posneta. Ostane mi samo še da zlepim datoteki R.txt in nolandolt,txt po stolpcih:
1 18.668 0.012 1.24078 R PG1633+099_ 14.396 0.0016 -0.191 0.0021 -0.085 0.0026
2 19.005 0.015 1.24078 R PG1633+099A 15.259 0.0032 0.871 0.0042 0.506 0.0033
3 17.608 0.007 1.24078 R PG1633+099G 13.749 0.0016 0.693 0.0012 0.412 0.0012
4 16.664 0.004 1.24078 R PG1633+099B 12.968 0.0016 1.081 0.0013 0.589 0.0010
5 17.526 0.006 1.24078 R PG1633+099F 13.768 0.0020 0.878 0.0024 0.523 0.0013
6 16.898 0.005 1.24078 R PG1633+099C 13.224 0.0017 1.144 0.0008 0.612 0.0010
7 17.618 0.007 1.24078 R PG1633+099D 13.689 0.0016 0.535 0.0018 0.324 0.0011
8 16.917 0.005 1.24078 R PG1633+099E 13.113 0.0021 0.841 0.0020 0.484 0.0014
11 16.569 0.004 2.076707 R 111_1925___ 12.387 0.0015 0.396 0.0012 0.226 0.0005
12 14.968 0.002 2.076707 R 111_1965___ 11.419 0.0018 1.710 0.0037 0.951 0.0010
13 14.586 0.002 2.076707 R 111_1969___ 10.382 0.0017 1.959 0.0014 1.177 0.0008
14 16.061 0.003 2.076707 R 111_2039___ 12.395 0.0021 1.369 0.0028 0.739 0.0021
15 16.683 0.004 2.076707 R 111_2088___ 13.193 0.0014 1.610 0.0042 0.888 0.0018
16 16.490 0.004 2.076707 R 111_2093___ 12.538 0.0025 0.637 0.0035 0.370 0.0032
11 17.008 0.004 2.15521 R 111_1925___ 12.387 0.0015 0.396 0.0012 0.226 0.0005
12 15.432 0.002 2.15521 R 111_1965___ 11.419 0.0018 1.710 0.0037 0.951 0.0010
13 15.350 0.002 2.15521 R 111_1969___ 10.382 0.0017 1.959 0.0014 1.177 0.0008
14 16.547 0.003 2.15521 R 111_2039___ 12.395 0.0021 1.369 0.0028 0.739 0.0021
15 17.192 0.004 2.15521 R 111_2088___ 13.193 0.0014 1.610 0.0042 0.888 0.0018
16 17.004 0.004 2.15521 R 111_2093___ 12.538 0.0025 0.637 0.0035 0.370 0.0032
18 15.787 0.004 2.881302 R 112_704____ 11.452 0.0030 1.536 0.0023 0.822 0.0021
19 16.292 0.005 2.881302 R 112_223____ 11.424 0.0007 0.454 0.0006 0.273 0.0005
20 16.873 0.007 2.881302 R 112_250____ 12.095 0.0021 0.532 0.0019 0.317 0.0019
21 14.464 0.002 2.881302 R 112_275____ 9.905 0.0001 1.210 0.0004 0.648 0.0004
22 17.027 0.007 2.881302 R 112_805____ 12.086 0.0006 0.151 0.0007 0.064 0.0006
23 16.096 0.005 2.881302 R 112_822____ 11.548 0.0007 1.030 0.0008 0.558 0.0005
# mag err X filter ime Vmag e_Vma B-V e_B-V V-R e_V-R
in to je za R končni rezultat fotometrije. Narišem v gnuplotu:
gnuplot> f(x)=a*x+b
gnuplot> fit f(x) 'R.txt' using 4:($7-$11 -$2) via a,b
gnuplot> plot 'R.txt' u 4:($7-$11-$2):($3+$8+$12) w errorbars ls 1 , f(x) ls 2
in dobim:
Ekstinkcijski koeficient v R barvi je 0.5. Iz grafa je razvidno, da dve zvezdi iz druge sekvence, to je SA 111 močno izstopajo. Potrebno bo še pogledat kaj je temu vzrok, mogoče da sta presvetljeni (saturirani), oziroma popraviti ali pa se jih izloči (cleaning) iz analize. Podobno narišemo še graf za V in B.
Še nekaj povezav:
http://spiff.rit.edu/classes/phys445/lectures/atmos/atmos.html